This paper presents an RFID based psychiatric patient tracking system in a psychiatric patient care center. In this system, RFID Field Generators and Readers are installed in the environment, near the entrance and exit points for tracking the patients. Every patient is required to wear the tag. When a tag receives the call from a Field generator, it responds to a Reader with the ID of the Field generator issuing the calling. Based on the Field Generator IDs a tag responds, the location of the patient associated with the tag can be approximately estimated. By so doing, not only the patient's moving patterns can be recorded but also the event of the patient leaving the main gate of the care center be detected. Besides the localization issue, in this paper we also employed a Graphic Coloring approach for solving the interference caused from Field Generator located one near another. Experimental results show that this algorithm has significantly improved the reliability of the tracking system.